Except that the TG16/TurboGrafx-16 is the American version of the PC Engine.
As for the question, there is no emulator for the PC-8801 or the PC-9801 that supports re-recording. However, it seems that at least Neko Project II/21 (PC-9801 emulator) can be used with Hourglass, which is what this TAS used, for instance.
Oh, there was already a video! Well, I also had thought using Hourglass like what you said, but I have no idea if submitting a movie using multiple tools is allowed. I haven't seen any precedent before. Is there any rules related of it?